Congenital elbow luxation
Congenital elbow luxation is a polygenic genetic disease of dogs characterized by lateral rotation of the proximal ulna and subluxation or luxation of the humeroulnar joint.
The cause of this condition is unknown, although some reports suggest an underlying hypoplasia or aplasia of the elbow ligaments, in particular the medial collateral ligament.
A breed predisposition has been noted in the Pug, Afghan Hound, Doberman, Dachshund, Yorkshire Terrier, Shetland Sheepdog, Boston Terrier, Miniature Poodle, Pomeranian, Chihuahua, Cocker Spaniel, Bouviers des Flandres, Jack Russell Terrier and English Bulldog.
Three types of congenital elbow luxation are recognized:
- Humeroradial - disruption of the humeroulnar joint with lateral rotation and subluxation or luxation of the ulna, with or without concurrent luxation of the radial head. Seen mainly in Pekingese, English bulldog, Shetland sheep-dog, Dachshund and Yorkshire terrier. It causes severe limb deformity and dysfunction.
- Humeroulnar - lateral or caudolateral luxation of the radial head, with the ulna in a relatively normal position - primarily affects Dachshunds.
- Combined humeroradial and humeroulnar - secondary to generalized joint laxity or polyarthrodysplasia and often occurs with multiple congenital abnormalities, including ectrodactyly (congenital splitting of the limb), patellar luxation, hydrocephalus, retained testicle, deformed tail and Legg-Calve-Perthes disease. In some cases of CEL, the medial collateral ligament is entirely absent.
This condition may occur unilaterally but in most dogs affects both elbows with disproportionate shortening and caudolateral subluxation or luxation of the radial head. Most elbow luxations occur laterally, but luxation can also occur medially.
Clinically affected dogs present at 3 - 4 months of age, and include pronation of the antebrachium, a partially flexed elbow, valgus deformity of the carpus, and an easily palpable radial head on the lateral aspect of the elbow are common findings. Some dogs exhibit only a mild lameness, while others cannot bear weight normally on the affected limb. Secondary osteoarthritis is common in chronic cases.
Radiographs usually show a poorly defined medial coronoid processes and osteoarthritis of the elbow joint, cranial bowing of the olecranon, and disturbed growth in length of the ulna with sharply demarcated spurs visible in affected dogs.
A differential diagnosis would include elbow dysplasia, hemimelia (congenital segmental deficiency of the radius or ulna), ectrodactyly (congenital splitting of the limb), previous fracture and malunion of the limb, osteochondritis dissecans, nutritional secondary hyperparathyroidism, rickets and ununited anconeal process.
Treatment of mild cases may be treated conservatively with frequent radiographic evaluation. The development of pain, progressive subluxation of the elbow, or bone remodeling are indications for surgical intervention. The more severe the condition and the longer it persists without treatment, the more guarded the prognosis and the more likely that arthritic change will occur.
Surgical reduction and stabilisation usually provides adequate clinical restoration of elbow movement with a goal of returning the limb to normal function rather than full joint reconstruction. This is usually achieved with closed manual reduction of the radial head luxation and ulnar ostectomy to allow unimpeded radial growth. Percutaneous temporary placement of a transarticular pin after closed reduction of the congenitally luxated joint has been reported to result in normal elbow function, with no development of degenerative joint disease or epiphyseal injury postoperatively.
More severe cases may require stronger stabilization, such as the use of bone plates, external fixators, or by screwing the proximal radius and ulna together. Elbow arthrodesis successfully alleviates pain but does cause a marked mechanical limp. However, arthrodesis of the elbow joint may be a superior alternative to amputation.
Because of the underlying genetic predispostion to this disease, breeding from affected dogs is not recommended.
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